North Korea’s move toward a rocket capable of reaching the U.S. mainland would justify tougher sanctions after consultations with the U.S., a presidential official told reporters on Tuesday. But he added Moon’s red line was an “abstract concept” for now.

On the flip side, it would be hard for Moon to move quickly toward talks with Kim as that is premised on a freeze in North Korea’ weapons program, said the official, who asked not be identified due to the sensitivity of the topic.

The lack of a clear plan from the new administration leaves Moon, a former human rights lawyer in office since May, in danger of playing a lesser role over his reclusive, nuclear-armed neighbor. Kim has already directed his recent rhetoric at the U.S., promising to send more "gifts" Donald Trump’s way.

Moon will meet with other leaders at the Group of 20 summit in Germany this week, where collective condemnations are expected of Kim’s actions, while South Korea and the U.S. conducted a joint missile drill on Wednesday. Meeting with German Chancellor Angela Merkel in Berlin on Wednesday, he said the pace of Pyongyang’s weapons development was a concern.

Still, his attempts to sound forceful against North Korea while also urging caution against rash action, and the lack of clarity on his “red line,” risk appearing wishy-washy at home. With popularity ratings around the 80 percent mark, expectations are high domestically for Moon to improve on the prior administration, where the president was impeached.

"The ICBM test has put both Moon’s popularity and his North Korea policies on a test board," said Lee Jae-mook, who teaches political science at Hankuk University of Foreign Studies in Seoul.

Kim’s advances in weapons technology "create a lot of homework for Moon," particularly if the tensions spill over to South Korea’s economy or people start to feel less safe, said Kim Yun-cheol, who teaches political science at the Humanitas College of Kyung Hee University.

Moon is already facing some pressure.

Choung Tae-ok, the floor spokesman for the main opposition Liberty Korea Party, said that Moon would end up doing "nothing" if he sticks to his dual approach of sanctions and dialogue. Lee Hye-hoon, leader of the opposition Bareun Party, called on Moon to conduct a "fundamental review" of his policies.

Support Ratings

Just one percent of those who approved of Moon in a Gallup Korea poll last week said they support him for his North Korea policies, while a further one percent favor him for his diplomacy. Among those who disapproved, a combined 17 percent said they did so for his North Korea policies, diplomacy, or a controversy over a U.S. missile shield.

"Moon’s desires notwithstanding, Pyongyang has no interest in discussing nuclear matters with the South,” said Ralph Cossa, president of the Pacific Forum CSIS in Honolulu. Kim wants to talk with the U.S. as “one nuclear power to another,” he said.

"Moon has been willing to talk tough to keep Trump on his side, but I’m not sure he is prepared to play the kind of hardball that would be required to really bring Kim to his senses."

Just two days before the missile test, Moon returned from Washington after meeting with Trump. Moon said the U.S. leader had handed him the keys to lead a push against Kim’s nuclear ambitions, allowing him to embark on "a long journey to build an eternal peace system" on the Korean peninsula.

‘Proposed Conditions’

But Shin Beomchul, a professor at the Korea National Diplomatic Academy, said the chances of inter-Korean talks are fading. "With the success of the ICBM, the North will ask for a higher level of compensation and Moon would find it difficult to meet all of the proposed conditions," Shin said.

Namkoong Young, who has taught inter-Korean politics at Hankuk University of Foreign Studies for more than 25 years, said one of the few choices left for Moon is to stress and strengthen South Korea’s alliance with the U.S.

"There are few things we can do alone,” other than “asking the friend with the muscle to do something for us," Namkoong said. Moon’s hope to resolve the nuclear issue through talks with Kim "sounds too idealistic to me.”